Median value, definition

Thus, if a soil contained lOOOmg/kg of a metal then the concentration would be 8 mg/kg, with a range of 1.3 to 50.2 mg/kg in crops corresponding median values of the levels of metal in soil were 10 000 mg/kg and 100 000 mg/kg, respectively, at the 80 and 800 mg/kg levels. These levels would definitely be of environmental concern (see the maximum levels of manganese (2750 mg/kg), iron (77500mg/kg), arsenic (1375mg/kg), titanium (8600mg/kg) and aluminium (85 000 mg/kg) found in crops, as reported in Table 11.1. 

Eor each method, DLs are taken from several (2-10) different references, typically interpreted as the number of references consulted, from which data were extracted, but occasionally as a combination of the reference consulted and those listed therein some duplication of information is to be expected. Values are different due to different instruments, conditions, definitions (2 s, 3 s, etc.) which were not rationalized to a common basis but accepted as is. Estimation of DLs is just that, an estimation from measurements with an RSD in the vicinity of 50%, negating, in this author s opinion, the need for very firm decisions on a uniform measurement basis. Eor each element, a best (lowest) DL was selected and a median value was calculated from the range of values tabulated median values (with some rounding) were selected for listing in this table as a representation of typical detection limits. 

The same can be said for mercury, even though the higher detection limit (10 ng/ml) renders the estimated median value of the population even less definite. However, the analytical sensitivity is sufficient to place our data within the range of variation of normal human blood, probably in the lower part. 

The clinical usefulness of MAC is questionable since, by definition, 50% of those receiving that concentration move in response to noxious stimulation. The median anaesthetic doses (ADs) required to prevent movement in 50% (AD50) and 95% (AD95) of patients are a later development and range from 5% to 40% greater than the MAC value. Again, these values are of only limited practical value. 

Data reduction involves the mathematical procedures applied to the results returned by the participants. Usually, there is a procedure to identify outliers - results that are remote from the anticipated value, probably caused by a transcription error or analysis of a different sample. As inclusion of these results could distort subsequent calculations it is useful to apply a statistical routine (e.g., greater than 3SDs from the mean) to eliminate these data. The trimmed data are then taken through the chosen calculations that, with few exceptions, are determination of the number and range of results, the mean, SD, and CV. If it is suspected or has been definitely shown that the distribution of data is not normal, the median should be found. In schemes where there are hundreds of participants, subroutines are included to re-examine results and present these calculations for a specific method or other variable. 

Fig. 7.8 Cumulative probability of survival at 1 million cycles for all four zirconia materials. Dashed lines denote the sandblasted groups. All four materials demonstrated a definite shift to the right as sandblasting improved their probability of survival. The median (50 % at 106 cycles) survival values Iot the as received and CoJet sandblasted groups were as follows LV = 743 MPa, LVs = 908 MPa, LVB = 635 MPa, LVBs = 809 MPa, KV = 593 MPa, KVs = 676 MPa, ZW = 549 MPa, ZWs = 587 MPa. The increase for Zeno (ZW) (green—far left) was not statistically significant (p = 0.295) [26]. With kind permission of Elsevier...

Assessment and prognostic value of the European LeukemiaNet criteria for clinicohematologic response, resistance and intolerance to HU in PV is now examined, and the criteria of response and definition were, actually, proposed by the Upper Limits of Normal (ULN). Such criteria were evaluated in 261 PV patients (median follow-up, 7.2years) treated with HU for a median of 4.4years. Complete response, partial response and no response were observed in 24%, 66% and 10% of patients, respectively... 

Development of a site dependent median (if mean values are chosen, a target probability one order of magnitude lower can be chosen) external event hazard definition in terms of the probabihty of exceedance for the annual frequency ... 

It is obvious that in Eqs. 1.10 - 1.13, when x is different, it will result in different values of the standard deviation, skewness and kurtosis. In general, these values are all different between arithmetic statistics and geometric statistics. From the definitions of arithmetic mean, median, and mode, one can predict that for positively skewed distributions that account for most of the industrial particulate systems, mode < median < mean. The degree of spread in these three values depends on the symmetry of the distribution. For completely symmetric distributions, these three values overlap. 

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